Star-shaped cutting insert for a front and back chamfering rotary milling cutter

Abstract

A front and back chamfering rotary milling cutter includes a cutter body including an insert pocket and a star-shaped indexable cutting insert releasably retained in the pocket. The cutting insert has star-shaped upper and lower surfaces connected by a peripheral surface intersecting each of the upper and lower surfaces. The cutting insert includes a plurality of circumferentially alternating inner and outer corner portions. A cutting portion is defined by each outer corner portion together with an adjacent first inner corner portion rotationally forward thereof and an adjacent second inner corner portion located rotationally rearward thereof. Each cutting portion includes a front chamfering cutting edge extending from the outer corner portion to the first inner corner portion and a back chamfering cutting edge extending from the outer corner portion to the second inner corner portion.

What is claimed is: 
     
       1. A front and back chamfering rotary milling cutter ( 20 ), having an axis of rotation (A) around which the rotary milling cutter ( 20 ) rotates in a direction of rotation (R), the axis of rotation (A) extending in a forward (D F ) to rearward direction (D R ), the rotary milling cutter ( 20 ) comprising:
 a cutter body ( 22 ) comprising an insert pocket ( 30 ); and 
 a star-shaped cutting insert ( 32 ) releasably retained in the insert pocket ( 30 ), the cutting insert ( 32 ) comprising:
 opposing insert top and bottom surfaces ( 42 ,  44 ) and an insert peripheral surface ( 46 ) extending therebetween; 
 a centrally located insert axis (C) extending through the insert top and bottom surfaces ( 42 ,  44 ); 
 circumferentially alternating outer and inner corner portions ( 50 ,  52 ), the inner corner portions ( 52 ) being located closer to the insert axis (C) than the outer corner portions ( 50 ); wherein
 each outer corner portion ( 50 ) together with an adjacent first inner corner portion ( 52   a ) rotationally forward thereof and an adjacent second inner corner portion ( 52   b ) located rotationally rearward thereof define a cutting portion ( 54 ); 
 each cutting portion ( 54 ) comprising a cutting edge ( 58 ) formed at the intersection of the insert top and peripheral surfaces ( 42 ,  46 ); and 
 the cutting edge ( 58 ) comprises:
 a front chamfering cutting edge ( 58   a ) extending from the outer corner portion ( 50 ) to the first inner corner portion ( 52   a ); 
 a back chamfering cutting edge ( 58   b ) extending from the outer corner portion ( 50 ) to the second inner corner portion ( 52   b ); and 
 a curved non-operative corner edge ( 66 ) extending between the front and back chamfering cutting edges ( 58   a ,  58   b ). 
 
 
 
 
     
     
       2. The rotary milling cutter ( 20 ) according to  claim 1 , wherein:
 the outer and inner corner portions ( 50 ,  52 ) are distanced at two different radii, an outer radius (R O ) and an inner radius (R I ), from the insert axis (C), respectively. 
 
     
     
       3. The rotary milling cutter ( 20 ) according to  claim 2 , wherein the cutting insert ( 32 ) exhibits rotational symmetry about the insert axis (C). 
     
     
       4. The rotary milling cutter ( 20 ) according to  claim 1 , wherein the cutting insert ( 32 ) is double-sided and each cutting portion ( 54 ) comprises an additional cutting edge ( 58 ) formed at the intersection of the insert bottom and peripheral surfaces ( 44 ,  46 ). 
     
     
       5. The rotary milling cutter ( 20 ) according to  claim 1 , wherein at least one of the front and back chamfering cutting edges ( 58   a ,  58   b ) are straight. 
     
     
       6. The rotary milling cutter ( 20 ) according to  claim 1 , wherein the insert pocket ( 30 ) is located at a forward end of the cutter body ( 22 ). 
     
     
       7. The rotary milling cutter ( 20 ) according to  claim 1 , wherein a first length (L 1 ) of the non-operative corner edge ( 66 ) is less than 25% of a second length (L 2 ) of either the front or back chamfering cutting edges ( 58   a ,  58   b ). 
     
     
       8. The rotary milling cutter ( 20 ) according to  claim 1 , wherein:
 the cutter body ( 22 ) comprises a shank peripheral surface ( 26 ) extending circumferentially around the axis of rotation (A); 
 the front and back chamfering cutting edges ( 58   a ,  58   b ) of one of the cutting portions ( 54 ) are disposed radially outwardly with respect to the shank peripheral surface ( 26 ), defining an active cutting portion ( 68 ). 
 
     
     
       9. The rotary milling cutter ( 20 ) according to  claim 8 , wherein the front and back chamfering cutting edges ( 58   a ,  58   b ) of the remaining cutting portions ( 54 ) are disposed radially inwardly with respect to the shank peripheral surface ( 26 ), defining a plurality of non-active cutting portions ( 70 ). 
     
     
       10. The rotary milling cutter ( 20 ) according to  claim 8 , wherein:
 in a side view of the rotary milling cutter ( 20 ), a bisector angle (β) is formed with the rearward direction (D R ) of the axis of rotation (A) and a bisector (B) of the outer corner portion ( 50 ) of the active cutting portion ( 68 ); and 
 the bisector angle (β) is in range 70°≤(β)≤110°. 
 
     
     
       11. The rotary milling cutter ( 20 ) according to  claim 10  wherein the bisector angle (β) is exactly 90°. 
     
     
       12. The rotary milling cutter ( 20 ) according to  claim 1 , wherein:
 the cutting insert ( 32 ) comprises exactly N cutting portions ( 50 ); and 
 N is greater or equal to 3 and less than or equal to 9. 
 
     
     
       13. The rotary milling cutter ( 20 ) according to  claim 12 , wherein N is equal to 5. 
     
     
       14. The rotary milling cutter ( 20 ) according to  claim 12 , wherein N is an odd number. 
     
     
       15. The rotary milling cutter ( 20 ) according to  claim 14 , wherein the rotary milling cutter ( 20 ) comprises exactly one cutting insert ( 32 ). 
     
     
       16. The rotary milling cutter ( 20 ) according to  claim 15 , wherein
 the cutter body ( 22 ) comprises a shank peripheral surface ( 26 ) extending circumferentially around the axis of rotation (A); 
 the shank peripheral surface ( 26 ) has a shank diameter (S); 
 in a side view of the rotary milling cutter ( 20 ), the insert axis (C) is distanced from the axis of rotation (A) by an axis distance (D); and 
 the axis distance (D) is less than 25% of the shank diameter (S). 
 
     
     
       17. The rotary milling cutter ( 20 ) according to  claim 1 , wherein the rotary milling cutter ( 20 ) comprises exactly one cutting insert ( 32 ). 
     
     
       18. The rotary milling cutter ( 20 ) according to  claim 17 , wherein
 the cutter body ( 22 ) comprises a shank peripheral surface ( 26 ) extending circumferentially around the axis of rotation (A); 
 the shank peripheral surface ( 26 ) has a shank diameter (S); 
 in a side view of the rotary milling cutter ( 20 ), the insert axis (C) is distanced from the axis of rotation (A) by an axis distance (D); and 
 the axis distance (D) is less than 25% of the shank diameter (S). 
 
     
     
       19. The rotary milling cutter ( 20 ) according to  claim 18 , wherein
 the shank peripheral surface ( 26 ) has a shank diameter (S); 
 the outer corner portions ( 50 ) define an imaginary outer circle (OC) having an insert diameter (ID); and 
 the insert diameter (ID) is larger than the shank diameter (S). 
 
     
     
       20. A double-sided star-shaped cutting insert ( 32 ), comprising
 opposing insert top and bottom surfaces ( 42 ,  44 ) and an insert peripheral surface ( 46 ) extending therebetween; 
 a centrally located insert axis (C) extending through the insert top and bottom surfaces ( 42 ,  44 ), the cutting insert ( 32 ) being indexable on each of the insert top and bottom surfaces ( 42 ,  44 ) about the insert axis (C); 
 circumferentially alternating outer and inner corner portions ( 50 ,  52 ), the inner corner portions ( 52 ) being located closer to the insert axis (C) than the outer corner portions ( 50 ); 
 a plurality of cutting portions ( 54 ), each cutting portion ( 54 ) defined by one of said outer corner portions ( 50 ), an adjacent first inner corner portion ( 52   a ) rotationally forward thereof and an adjacent second inner corner portion ( 52   b ) located rotationally rearward thereof; 
 a median plane (M) passing through the insert peripheral surface ( 46 ) midway between the top and bottom surfaces ( 42 ,  44 ); 
 a bisector plane (PS) formed at each cutting portion ( 54 ), each bisector plane (PS) containing the insert axis (C), and bisecting both an associated outer corner portion ( 50 ) and an associated opposite inner corner portion ( 52 ); 
 a median axis (AS) formed at an intersection of each bisector plane (PS) and the median plane (M), each median axis (AS) intersecting the insert axis (C), and passing through both an associated outer corner portion ( 50 ) and an associated opposite inner corner portion ( 52 ); wherein: 
 each cutting portion ( 54 ) comprising a cutting edge ( 58 ) formed at the intersection of the insert top and peripheral surfaces ( 42 ,  46 ); 
 each cutting edge ( 58 ) comprises:
 a front chamfering cutting edge ( 58   a ) extending from the outer corner portion ( 50 ) to the first inner corner portion ( 52   a ); 
 a back chamfering cutting edge ( 58   b ) extending from the outer corner portion ( 50 ) to the second inner corner portion ( 52   b ); and 
 a curved non-operative corner edge ( 66 ) extending between the front and back chamfering cutting edges ( 58   a ,  58   b ); 
 
 the cutting insert ( 32 ) has a number N cutting portions and is N-way indexable on both the top and bottom surfaces, N being 3, 5, 7 or 9; 
 the cutting insert ( 32 ) is mirror symmetrical about the median plane (M); 
 the cutting insert ( 32 ) is mirror symmetrical about each bisector plane (PS); 
 the cutting insert ( 32 ) is 180° rotationally symmetrical about each median axis (AS); and 
 the cutting insert ( 32 ) is devoid of cutting edges which extend between top and bottom surfaces ( 42 ,  44 ) in a thickness direction of the cutting insert ( 32 ) parallel to the insert axis (C). 
 
     
     
       21. The cutting insert ( 32 ) according to  claim 20 , where N is equal to 5. 
     
     
       22. The cutting insert ( 32 ) according to  claim 20 , wherein a first length (L 1 ) of the non-operative corner edge ( 66 ) is less than 25% of a second length (L 2 ) of either the front or back chamfering cutting edges ( 58   a ,  58   b ). 
     
     
       23. The cutting insert ( 32 ) according to  claim 20 , wherein in a plan view of the cutting insert ( 32 ) the front chamfering cutting edge ( 58   a ) on any given cutting portion ( 54 ) and the adjacent back chamfering cutting edge ( 58   b ) rotationally forward thereof converge towards each other in a radially inward direction with respect to the insert axis (C). 
     
     
       24. A front and back chamfering rotary milling cutter ( 20 ), having an axis of rotation (A) around which the rotary milling cutter ( 20 ) rotates in a direction of rotation (R), the axis of rotation (A) extending in a forward (D F ) to rearward direction (D R ), the rotary milling cutter ( 20 ) comprising:
 a cutter body ( 22 ) comprising an insert pocket ( 30 ); and 
 a cutting insert ( 32 ) in accordance with  claim 20  releasably retained in the insert pocket ( 30 ). 
 
     
     
       25. The rotary milling cutter ( 20 ) in accordance with  claim 24 , wherein:
 the cutter body ( 22 ) comprises a shank peripheral surface ( 26 ) extending circumferentially around the axis of rotation (A); 
 the front and back chamfering cutting edges ( 58   a ,  58   b ) of one of the cutting portions ( 54 ) are disposed radially outwardly with respect to the shank peripheral surface ( 26 ), defining an active cutting portion ( 68 ); and 
 in a side view of the rotary milling cutter ( 20 ), a bisector angle (β) is formed with the rearward direction (D R ) of the axis of rotation (A) and a bisector (B) of outer corner portion ( 50 ) of the active cutting portion ( 68 ); and 
 the bisector angle (β) is in range 70°≤(β)≤110°.